You hit inconsistently, hook, or slice the ball without a known cause.
Check the position of the back of your lead hand during contact. You want it and the clubface to be aimed at target as you make contact with the ball.
Watch other players that are hooking, slicing, or hitting unpredictably. Look to see where their forward hand is aimed. If the back of their lead hand is facing towards the ground, you will likely see a hook. If it is facing towards the sky, you will likely see a slice. Now practice swinging a mid iron and focus on trying to have your forward hand square to the target at impact so that it is aimed in the same direction as the clubface is aimed. An easy drill to reinforce this feeling is to swing without a club with your forward shoulder against a wall or golf cart. Take your arms back as if you had a club in your hands. Swing forward and allow your lead hand to slap the wall or cart. Whenever you feel you are turning your hands over too much or not enough, use the image of slapping something with the back of your forward hand to help you square it at impact.
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